I boiled off around 400 gallons of maple sap over a weekend last February with a 60' blue spruce providing the fuel.........now mind you it was green and in an outside evaporator, and it STILL blew me away with the amount of heat it put out! Split it, stack it, season it a year and you'll be loving the heat it puts out!!

We have blue spruce all around us, and we have at least one a year die or blow over in high winds [the latter is always due to weakened trunk from beetle infestation]. Often, I find that the recently-dead/blown down ones are sappier than one would expect. Because the tree was fighting the beetles. Anyhow, this makes the wood even heavier than usual. Our trees reach well above 100 ft. tall and 28-30"+ diameter. So, a round cut to firewood length is way beyond my ability to roll it into my truck. I quarter the rounds with the saw, then either let the pieces sit in the woods a couple months or split them with my splitter. They season, up here, in a couple months or so once I have the wood split [10-15% humidity normal here].

They burn fine. The wood does not burn as hot as ponderosa pine or lodgepole. Well, I have never measured it, but I can easily tell. But it is wood, and one tree will give you a lot of firewood.

I had one that died on me, around 30 foot tall, that I cut down and bucked. I let it sit for a year before getting around to splitting it. Well, it's a darn good thing I have a chain saw, as I think I pretty well had to rip most of the trunk pieces. What a bugger to split. It had more knots that a Danish bakery. It burned good and hot though.